Matthew Hertgen, the New Jersey man accused in the disturbing death of his younger brother earlier this year, has died while being held at Mercer County Jail, authorities confirmed.
According to officials, the 32-year-old was found unresponsive on May 8 inside the jail facility in Hopewell Township, New Jersey. Early reports indicate the death is being investigated as an apparent suicide, though an official cause of death is pending autopsy results.
Hertgen’s death came just weeks after a judge ruled that he was legally insane and therefore not criminally responsible in connection with the death of his 26-year-old brother, Joseph Hertgen, in February 2025.
The case drew widespread attention due to its disturbing details and the severe mental health concerns raised during court proceedings.
Prosecutors previously alleged that Matthew attacked his brother inside a Princeton apartment using a knife and a golf club before also killing the family cat and setting it on fire. Investigators later uncovered graphic evidence inside the residence during the investigation.
During hearings earlier this year, forensic psychologist Dr. Gianni Pirelli testified that Matthew had been suffering from severe psychosis and religious delusions for years. According to testimony, he experienced intense visions and believed he was involved in a battle tied to apocalyptic or spiritual themes.
Court documents also revealed that family members had been deeply concerned about his deteriorating mental condition long before the tragedy occurred. Matthew’s older brother reportedly warned Joseph on the day of the incident that Matthew was having frightening “visions” and asked him to reach out if he needed help.
Following the judge’s insanity ruling in March, a future hearing had been scheduled to determine whether Matthew would remain in a secure psychiatric facility or another form of supervised custody.
In an obituary published after his death, Hertgen’s family focused heavily on his long battle with mental illness and encouraged donations to NAMI Mercer, a nonprofit organization supporting individuals and families affected by mental health conditions.
“Growing up, Matthew is remembered as a caring and loving person,” the obituary stated. It also noted that he graduated from Wesleyan University, where he played soccer, before later building a successful career in finance.
The family added that despite his struggles in later years, Matthew expressed “sorrow, remorse, and repentance,” and remained surrounded by the support and forgiveness of loved ones.
The tragic case has reignited online discussions surrounding severe mental illness, family intervention, and the challenges families face when loved ones experience psychotic episodes.
